Which of the following is superoxide?

The fourth period ends with the element ____

The p-block elements along with s-block elements are called as ____ elements.

The property of every eight elements is similar to that of the 1st element. This is proposed by _______

The elements, Unnilhexium and Seaborgium are the same.

Which of the following period is the shortest one?

In the modern long-form of periodic table, the horizontal rows and the vertical columns are called as ______ and _______…

Ionization energies are always positive.